1. Field of Invention
The invention relates to a braking force control apparatus for a vehicle, and more particularly, to a braking force control apparatus for a vehicle which has a regenerative braking device and a frictional braking device and in which anti-skid control is performed.
2. Description of Related Art
A braking force control apparatus for an automobile or the like having a regenerative braking device and a frictional braking device is disclosed, for example, in Japanese Patent Application No. 2000-62590, which is one of the applications filed by the present applicant. In a vehicle having a regenerative braking device and a frictional braking device, the sum of a regenerative braking force and a frictional braking force is applied to the vehicle as a total braking force. A braking force control apparatus according to a known related art is designed to set the regenerative braking force as 0 and make supplementation with a braking force corresponding to a regenerative braking force that has been reduced by a frictional braking device.
According to such a braking force control apparatus, if a braking slip amount in a certain wheel becomes excessively great, anti-skid control is started as to the wheel. Because the regenerative braking force applied to the wheel becomes equal to 0, anti-skid control is performed suitably without adversely affecting the regenerative braking force. Even if the regenerative braking force has become equal to 0, an abrupt decrease in deceleration of the vehicle at the beginning of anti-skid control is suppressed as compared to the case where the braking force generated by the frictional braking device is not supplemented with the braking force corresponding to the regenerative braking force that has become equal to 0.
However, according to a conventional braking force control apparatus as described above, the regenerative braking force is reduced to 0 abruptly as soon as anti-skid control is started. However, it is difficult to precisely and duly supplement the reduced regenerative braking force with a braking force corresponding to an amount of decrease in the regenerative braking force by means of the frictional braking device. Accordingly, an abrupt fluctuation in deceleration of the vehicle, which is caused by reducing the regenerative braking force to 0 at the beginning of anti-skid control, cannot be suppressed effectively. An improvement must be made in this respect to enhance driveability of the vehicle.